1. Field Of The Invention
This invention relates to warp sizes and more specifically it relates to an improved warp size for filament yarns based upon polyvinyl alcohol.
2. Description Of The Prior Art
Polyvinyl alcohol (PVA) has been tried, repeatedly as a warp size for polyester filament yarn but has been rejected due to the undesirable quantity of "shed" that accumulates on the loom. This "shed" consists of fragments of the size that are scraped off the individual yarns by the various areas of high abrasion encountered in weaving, for example the reciprocating action of the reed. As a consequence of this serious problem, PVA is not used as a principle ingredient in polyester filament yarn sizing.
Although urea has been used in conjunction with PVA in warp sizing of spun yarns for several years, this combination is not an acceptable warp size for filament yarns because of the excessive crystallization of urea on the surface of cast films, resulting in powdery shedding and because of the poor viscosity stability in concentrated solutions.
C. R. Williams and D. P. Donermeyer disclosed in the American Dyestuff Reporter, June 3, 1968, the addition of sucrose to PVA in order to increase rate of removal of warp size.
Nippon Gohsei disclosed in Japanese Patent Application JA-134571, published on July 7, 1977 the addition of 0.5-5.0 weight percent of mono- or disaccharide, such as glucose, fructose, sucrose and maltose, to aqueous PVA solutions thereby preventing size shedding, fluffing and end-breakage of the warp during weaving. The solids content of the solution was 5-11 weight percent.
United States Patent Application Ser. No. 640,782, filed on Dec. 15, 1975, and now abandoned discloses adhesive compositions that are combinations of (1) polyvinyl alcohol, (2) a crystalline solvent such as urea and (3) a viscosity reducing diluent such as water, liquid polyhydric compounds such as glycols, etc., and optionally extenders, such as starch, clay, etc. These adhesives are disclosed to be suitable for cellulosic substrates providing excellent ambient temperature water resistance while being fully repulpable in hot water. Application of such a combination of PVA, urea and polyhydric alcohol to polyester filament yarns gives very soft, flexible films which tend to cause end-to-end, i.e., yarn-to-adjacent yarn adhesions. Abrasion resistance is only marginal to poor.